Edexcel Biology B is very scarce when it comes to finding information on it online. I've taken it upon my self to publish my own notes to help fellow students that have a hard time understanding the subject. The information in the text book is very large and can be hard to narrow down to a particu...
i Understand that mutations are the source of new variations and that the processes of
random assortment and crossing over during meiosis give rise to new combinations of
alleles in gametes.
Mutation are sources of variation as they can introduce advantageous alleles due to
environmental changes.
Random assortment is when chromosome pairs from the mother and father are distributed
randomly into gametes.
Crossing over- this takes place during meiosis when large multi-enzyme complexes ‘cut and
join’ bits of the material and paternal chromatids. This leads to added genetic variation as
many new combinations of alleles.
, ii Understand how random fertilisation during sexual reproduction brings about genetic
variation.
Random fertilisation introduces genetic variation as the male and female gametes form two
unrelated individuals fuse. there are lots of different combinations of gametes which can fuse
into the zygote
8.2 transfer of genetic information
i Understand the terms ‘genotype and phenotype’,’ homozygote and heterozygote’,
‘dominance’, ‘recessive’, ‘codominance’ and ‘multiple alleles’.
Homozygote- an individual where both of the alleles coding for a particular trait are identical
Heterozygous- an individual where where two of the alleles coding for a particular trait are
different
dominance -A phenotype that is expressed when one allele codes for it.
Recessive- A phenotype that is expressed when both alleles code for phenotype.
Codominant- When alleles are codominant both alleles and their phenotype are expressed
Multiple alleles- There are more then two possible variants at a particular locus
ii Be able to construct genetic crosses and pedigree diagrams.
Monohybrid Cross
When one gene is considered at a time it is referred to as monohybrid cross
Wrinkle and smooth pea
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